Mesh unwraps in undesired way (seams are not obeyed)
Your mesh has some problems.  You have not joined the wing to the body correctly which has left unconnected edges and interior faces. This is the cause of the extra UV islands.

You can see the problem area by clicking Select -> Select All By Trait -> Non-manifold.  You should remove the interior faces and connect the wing to body for the mesh to unwrap properly.

You also have several nasty poles that may affect the way the mesh deforms once rigged.  If you are intending to fix these, it might be worth altering the topology before you UV the mesh.